Generally, rotary atomizing head type coating apparatus are widely resorted to in coating work pieces such as vehicle bodies or the like. In this regard, lately there are increasing demands for coating apparatus which can cut the amounts of paint and solvent to be discarded each time when changing the paint color and which can cope with a larger number of paint colors.
For instance, regarding rotary atomizing head type coating apparatus which are arranged to reduce the amounts of discarding paint and solvent and at the same time to cope with an increased number of paint colors, there has been known a coating apparatus as disclosed in Japanese Laid-Open Patent Publication No. H8-229446. This rotary atomizing head type coating apparatus employs a number of paint cartridges of different colors which are arranged to be replaceably loaded on the coating apparatus in the course of a coating operation on a vehicle body or bodies.
More specifically, the rotary atomizing head type coating apparatus just mentioned is largely constituted by a housing which is so shaped as to provide a coating machine mount portion on the front side and a cartridge mount portion on the rear side thereof, and a coating machine which is mounted on the coating machine mount portion of the housing, including an air motor with a rotational shaft and a rotary atomizing head which is mounted on the rotational shaft on the front side of the air motor. A feed tube passage hole is passed axially within the rotational shaft of the air motor of the coating machine, and said feed tube passage hole is into the rotary atomizing head at its fore end and opened into the cartridge mount portion of the housing at its rear end.
The coating apparatus is provided with a number of paint cartridges of different colors which are designed to be replaceably mounted on the cartridge mount portion of the housing. Each one of these paint cartridges is constituted by a container which is filled with paint, and a feed tube which is extended axially forward from a fore end of the paint container. The paint container is adapted to be replaceably set in position on the cartridge mount portion of the housing, with the feed tube passed into the above-mentioned feed tube passage hole.
Further, provided internally of each paint cartridge is a movable partition wall which divides the internal space of the cartridge into a paint chamber and an extruding air chamber, and an air passage which is provided on the part of the cartridge to supply extruding air to the extruding air chamber. Provided also on the part of the housing is an extruding air passage which is communicated with the extruding air passage on the side of the paint cartridge. Thus, through the extruding air passage on the side of the housing and the extruding air passage on the side of the paint cartridge, extruding air is supplied to the extruding air chamber to push the movable partition wall forward, thereby extruding the paint in the paint chamber into the rotary atomizing head through the feed tube.
In the case of the rotary atomizing head type coating apparatus which is arranged as described above, a paint cartridge of a desired color is selected from a group of paint cartridges of different colors, and set on the paint cartridge mount portion on the housing. Then, air is supplied to the extruding air chamber in paint cartridge to let the paint in the paint chamber of the cartridge spurt out toward the rotary atomizing head through the feed tube. As a result, paint is sprayed toward an object to be coated from the rotary atomizing head.
The paint color can be changed simply by replacing the paint cartridge by a cartridge of a desired color without discarding paint and solvent.
On the other hand, at the end of a coating operation, since a paint within a paint cartridge which has been dismantled for a change of paint color is more or less consumed and a paint need to be refilled in preparation for a next use.
In refilling used paint cartridges, it has been the general practice to use a paint refilling system. For example, a paint cartridge refilling system which is used in the above-mentioned prior art is provided with quick joints which are extended out from tap pipes of paint circulation system of different colors. Firstly, a used paint cartridge is dismantled from the housing and put on a refilling table for replenishing paint into a paint chamber of the cartridge. Then, the quick joint is connected to a paint supply port, which is provided on the cartridge separately from the feed tube, exclusively for refilling purposes.
Therefore, with the rotary atomizing head type coating apparatus which is described above, a paint supply post is provided on the cartridge separate from the feed tube and a paint is refilled into the cartridge from a paint supply post. Thereby, the construction of the paint cartridge becomes complicated and increases the production cost. In addition, it has a possibility to increase the position of paint leaks.
Namely, the prior art paint cartridge refilling system is arranged to replenish a paint cartridge by connecting a paint supply port of the cartridge to one of quick joints from a paint circulation piping system. The refilling system of this sort has problems or drawbacks in that it requires a lot of efforts in connecting a paint supply port to a quick joint and consumes a great deal of time for the connecting work.